Oxidative desulfurization of fuel oil

ABSTRACT

A method for purifying a sulfur-containing fuel oil comprising (a) contacting in a first reaction mixture the sulfur-containing fuel oil with an exogenous binary catalyst, hydrogen peroxide, and a water-soluble acid at a temperature in a range of from about 25° C. to about 150° C. to provide a first oxidized mixture; and (b) separating at least one oxidized sulfur compound from the first oxidized mixture to provide a purified fuel oil. The first reaction mixture may further comprise a phase transfer catalyst. Furthermore, the sulfur-containing fuel oil may be deasphalted prior to contacting with the catalyst, hydrogen peroxide, and the water-soluble acid.

BACKGROUND

The invention includes embodiments that generally relate to a method forpurifying sulfur-containing fuel oil using a catalyst, a water-solubleacid and a peroxide.

Raw/fossil fuels, such as fuel oil including a crude oil and oildistillates and refinery products like gasoline, kerosene, diesel fuel,naphtha, heavy fuel oil, natural gas, liquefied natural gas andliquefied petroleum gas, and like hydrocarbons, are useful for a numberof different processes, particularly as a fuel source, and mostparticularly for use in a power plant. Virtually all of these fuelscontain relatively high levels of naturally occurring, organic sulfurcompounds, such as, but not limited to, sulfides, mercaptans andthiophenes. Hydrogen generated in the presence of such sulfur compoundshas a poisoning effect on catalysts used in many chemical processes,particularly catalysts used in fuel cell processes, resulting inshortening the life expectancy of the catalysts. When present in a feedstream in a fuel cell process, sulfur compounds may also poison the fuelcell stack itself. Because of the relatively high levels of sulfurcompounds that may be present in many crude fuel feed streams, it isnecessary that these feed streams be desulfurized.

Furthermore, desulfurization of fuels has become an important problemdue to the upcoming regulatory requirements that require a reduction incurrent sulfur emissions. Two major tasks in the sulfur removal fromfuel include (i) the deep desulfurization of diesel fuel (reducing Scontent from ˜500 parts per million to below 15 parts per million) and,(ii) sulfur removal from crude and heavy fuel oils used for energyproduction (reducing S content from 3-4 percent to less than 0.5percent). Conventional hydrodesulfurization (HDS) method using hydrogenhave not only been insufficient to effect the deep desulfurization ofdiesel fuels but are also relatively expensive for the direct sulfurremoval from a crude and heavy fuel oils due to high cost of hydrogenand the use of high temperature and pressure. Alternatively oxidativedesulfurization (ODS) methods using oxidants like hydrogen peroxide,molecular oxygen or ozone, require somewhat less demanding operatingconditions when compared to the operating conditions employed in HDSmethods. Further, where oxygen may be used as the stoichiometricoxidant, ODS methods may be cost competitive with HDS methods.

Thus, there exists a need for efficient and cost effective ODS methodsfor sulfur removal from fuel, to provide desulfurized fuels that meetmodern engineering and regulatory standards.

BRIEF DESCRIPTION

In one embodiment, the present invention provides a method for purifyinga sulfur-containing fuel oil comprising: (a) contacting in a firstreaction mixture the sulfur-containing fuel oil with an exogenous binarycatalyst, hydrogen peroxide, and a water-soluble acid at a temperaturein a range of from about 25° C. to about 150° C.1 to provide a firstoxidized mixture; and (b) separating at least one oxidized sulfurcompound from the first oxidized mixture to provide a purified fuel oil.

In another embodiment, the present invention provides a method forpurifying a sulfur-containing fuel oil comprising (a) contacting in afirst reaction mixture the sulfur-containing fuel oil with a hydrocarbondiluent, an exogenous binary catalyst, hydrogen peroxide, and awater-soluble acid at a temperature in a range of from about 50° C. toabout 150° C. to provide a first oxidized mixture; and (b) separating atleast one oxidized sulfur compound from the first oxidized mixture; and(c) recovering the hydrocarbon diluent to provide a purified fuel oil.

In yet another embodiment, the present invention provides a method forpurifying a sulfur-containing fuel oil comprising (a) contacting in afirst reaction mixture the sulfur-containing fuel oil comprisingbenzothiophene, dibenzothiophene, alkyl substituted benzothiophenes, andalkyl substituted dibenzothiophenes with petroleum ether, an exogenousbinary catalyst, hydrogen peroxide, and a water-soluble acid at atemperature in a range of from about 50° C. to about 120° C. to providea first oxidized mixture comprising sulfoxides and sulfones ofbenzothiophene, dibenzothiophene, alkyl substituted benzothiophenes, andalkyl substituted dibenzothiophenes; (b) separating at least oneoxidized sulfur compound from the first oxidized mixture; and (c)recovering petroleum ether to provide a purified fuel oil.

These and other features, aspects, and advantages of the presentinvention may be understood more readily by reference to the followingdetailed description.

DETAILED DESCRIPTION

In the following specification and the claims, which follow, referencewill be made to a number of terms, which shall be defined to have thefollowing meanings.

The singular forms “a”, “an”, and “the” include plural referents unlessthe context clearly dictates otherwise. “Optional” or “optionally” meansthat the subsequently described event or circumstance may or may notoccur, and that the description includes instances where the eventoccurs and instances where it does not.

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about” and “substantially”, are not to be limited tothe precise value specified. In at least some instances, theapproximating language may correspond to the precision of an instrumentfor measuring the value. Here and throughout the specification andclaims, range limitations may be combined and/or interchanged, suchranges are identified and include all the sub-ranges contained thereinunless context or language indicates otherwise.

In one embodiment, the present invention provides a method for purifyinga sulfur-containing fuel oil comprising, (a) contacting in a firstreaction mixture the sulfur-containing fuel oil with an exogenous binarycatalyst, hydrogen peroxide, and a water-soluble acid at a temperaturein a range of from about 25° C. to about 150° C. to provide a firstoxidized mixture; and (b) separating at least one oxidized sulfurcompound from the first oxidized mixture to provide a purified fuel oil.

In one embodiment, the sulfur-containing fuel oil is a crude oil, forexample Saudi sweet crude oil, West Texas Intermediate crude oil, Dubaicrude oil, and Brent crude oil. In an alternate embodiment, thesulfur-containing fuel oil is a crude oil, which has been subjected toasphaltene removal. In one embodiment, the sulfur-containing fuel oil isa distillate or other refinery products of a crude oil like gasoline,kerosene, diesel fuel, naphtha, heavy fuel oil, natural gas, liquefiednatural gas and liquefied petroleum gas. In one embodiment, thesulfur-containing fuel oil comprises dibenzothiophene, benzothiophene,alkyl substituted dibenzothiophenes, and alkyl substitutedbenzothiophenes.

In one embodiment, the sulfur-containing fuel oil comprises less than 5weight percent sulfur based on the weight of sulfur-containing fuel oil.In another embodiment, the sulfur-containing fuel oil comprises lessthan 3 weight percent sulfur based on the weight of sulfur-containingfuel oil. In another embodiment, the sulfur-containing fuel oilcomprises less than 2 weight percent sulfur based on the weight ofsulfur-containing fuel oil.

As used herein the phrase “exogenous binary catalyst” means an “externalbinary catalyst” that is combined in a first reaction mixture with asulfur-containing fuel oil. In one embodiment, the exogenous binarycatalyst comprises a first component, a catalyst and a second component,a promoter. In one embodiment, the binary catalyst comprises a firstcomponent selected from the group consisting of phosphate salts, andoxides, acids and salts of molybdenum, tungsten, manganese, andcombinations thereof, and the second component is selected from thegroup consisting of oxides and salts of cerium, iron, vanadium,titanium, manganese, cobalt, nickel, copper and combinations thereof Inanother embodiment, the first component comprises an oxide or a salt ofmolybdenum. In another embodiment, the molybdenum containing firstcomponent is a molybdenum isopolyacid or heteropolyacid or its salt withdifferent cations, for example, ammonium or alkali metal. Theisopolyacid means a polyacid having a polynuclear structure wherein asingle oxo-acid is condensed. The heteropolyacid means a polyacid havinga polynuclear structure wherein two or more kinds of oxo-acids may becondensed. The heteropolyacid has a structure comprising a condensedstructure of an acid forming the skeleton (skeleton acid) and a smallnumber of other kinds of atoms (hetero atom) contained in the centerthereof and the like. In yet another embodiment, the first componentcomprises an oxide or a salt of manganese. In another embodiment, thesecond component comprises an oxide or a salt of cobalt. In yet anotherembodiment, the second component comprises an oxide or a salt of cerium.In still yet another embodiment, the second component comprises an oxideor a salt of iron.

In one embodiment, the exogenous binary catalyst may comprise oxides orsalts of molybdenum as the first component and oxides or salts of ceriumas the second component. In another embodiment, the binary catalyst maycomprise oxides or salts of manganese as the first component and oxidesor salts of iron, cobalt, or nickel as the second component. In yetanother embodiment, the binary catalyst may comprise a phosphate salt,for example ammonium hydrophosphate as the first component and oxides orsalts of iron, cobalt, or nickel as the second component.

In one embodiment, the total amount of the first component and thesecond component used in the first reaction mixture is in a range offrom about 0.5 weight percent to about 10 weight percent based on theamount of sulfur-containing fuel oil. In another embodiment, the totalamount of the first component and the second component used in the firstreaction mixture is in a range of from about 0.5 weight percent to about5 weight percent based on the amount of sulfur-containing fuel oil. Inyet another embodiment, the total amount of the first component and thesecond component used in the first reaction mixture is in a range offrom about 1 weight percent to about 3 weight percent based on theamount of sulfur-containing fuel oil.

In one embodiment, the atomic ratio of the first component to the secondcomponent is 6:1. In another embodiment, the atomic ratio of the firstcomponent is 9:1. In yet another embodiment, the atomic ratio of thefirst component to the second component is 12:1. In one embodiment, aphysical mixture of the first and the second components may be used asthe binary catalyst. In another embodiment, a pre-synthesized complexcompound comprising the first and the second components, for example aheteropolyanion salt may be used as the exogenous binary catalyst.

In one embodiment, the water-soluble acid may be selected from the groupconsisting of formic acid, acetic acid, propionic acid, butyric acid,sulfuric acid, phosphoric acid, and mixtures of two or more of theforegoing acids. In one embodiment, the acid is acetic acid. In anotherembodiment, the acid is formic acid. In yet another embodiment, the acidis sulfuric acid. In one embodiment, acetic acid anhydride may be usedto generate acetic acid in situ in the first reaction mixture.

In one embodiment, the amount of water-soluble acid employed in theoxidation reaction is in a range of from about 15 volume percent toabout 40 volume percent based on the amount of the sulfur-containingfuel oil. In another embodiment, the amount of water-soluble acidemployed in the oxidation reaction is in a range of from about 20 volumepercent to about 35 volume percent based on the amount of thesulfur-containing fuel oil. In another embodiment, the amount ofwater-soluble acid employed in the oxidation reaction is in a range offrom about 25 volume percent to about 30 volume percent based on theamount of the sulfur-containing fuel oil.

In one embodiment, the amount of hydrogen peroxide (calculated as 100percent) employed in the oxidation reaction is in a range of from about4 weight percent to about 20 weight percent based on the amount of thesulfur-containing fuel oil. In another embodiment, the amount ofhydrogen peroxide employed in the oxidation reaction is in a range offrom about 5 weight percent to about 15 weight percent based on theamount of the sulfur-containing fuel oil. In yet another embodiment, theamount of hydrogen peroxide employed in the oxidation reaction is in arange of from about 6 weight percent to about 10 weight percent based onthe amount of the sulfur-containing fuel oil. In one embodiment,hydrogen peroxide may be added as an aqueous solution having aconcentration in a range of from about 15 weight percent to about 30weight percent. In various embodiments, hydrogen peroxide may be addedto the first reaction mixture using methods known to one skilled in theart, such as for example, in a continuous manner or in portions.

In one embodiment, the at least one oxidized sulfur compound may beseparated from the first oxidized mixture using a solid-liquidextraction process, for example an adsorption process, to provide thepurified fuel oil. In one embodiment, the at least one oxidized sulfurcompound may be separated from the first oxidized mixture using aliquid-liquid extraction process, to provide the purified fuel oil. Oneskilled in the art can easily determine the process and the conditionsrequired to achieve satisfactory separation.

In one embodiment, the method for purifying the sulfur-containing fueloil further comprises a step of recovering the binary catalyst. In oneembodiment, the binary catalyst is recovered from the first oxidizedmixture by filtration or centrifuging/decantation, using methods knownto one skilled in the art.

In one embodiment, the first oxidized mixture is contacted with a poroussilica adsorbent material, wherein the adsorbent material ischaracterized by a Brunauer-Emmett-Teller (BET) surface area value(total) of at least about 15 m²/g; and a Barrett-Joyner-Halenda (BJH)pore volume (total) of at least about 0.5 cc/g. Such porous adsorbentmaterials and their use are described in copending U.S. patentapplication Ser. No. 11/934298 filed Nov. 2, 2007 which is incorporatedherein by reference in its entirety. In instances wherein thesulfur-containing fuel oil comprises other metallic impurities such asvanadium compounds, such contact results in removal of these othermetallic impurities or their oxidation products from the first oxidizedmixture.

In another embodiment, the first reaction mixture further comprises aphase transfer catalyst. In one embodiment, the phase transfer catalystcomprises a quaternary ammonium salt or a phosphonium salt. Non-limitingexamples of suitable phase transfer catalysts may be selected from thegroup consisting of methyltrioctylammonium chloride (Aliquat 336™),tetraalkylammonium bromide, trialkylmethylammonium bromide, andhexaethylguanidium bromide. In another embodiment, the phase transfercatalyst comprises a quaternary ammonium or a phosphonium saltcomprising an heteropolyanion M¹ _(n)M² _(m)O^(q) _(p), wherein M¹ isselected from the group consisting of phosphorus, cerium, vanadium,manganese, iron, and cobalt, M² is selected from the group consisting ofmolybdenum, tungsten and vanadium or their mixture, “n” is an integerhaving a value 1 to 2, “m” is an integer having a value 6 to 18, “p” isan integer having a value 24 to 62, and “q” is an integer having a value3 to 6.

In one embodiment, the amount of phase transfer catalyst used is in arange of from about 0.1 weight percent to about 10 weight percent basedon the amount of sulfur-containing fuel oil. In another embodiment, theamount of phase transfer catalyst used is in a range of from about 0.5weight percent to about 1 weight percent based on the amount ofsulfur-containing fuel oil. In yet another embodiment, the amount ofphase transfer catalyst used is in a range of from about 1 weightpercent to about 3 weight percent based on the amount ofsulfur-containing fuel oil.

In one embodiment, the temperature at which the oxidation (also referredto as contacting the fuel oil with an exogenous binary catalyst,hydrogen peroxide, and an acid at a temperature in a range of from about25° C. to about 150° C., to provide a first oxidized mixture) is carriedout is in a range of from about 25° C. to about 110° C. In anotherembodiment, the temperature at which the oxidation is carried out is ina range of from about 55° C. to about 95° C. In yet another embodiment,the temperature at which the oxidation is carried out is in a range offrom about 60° C. to about 90° C.

In another embodiment, the sulfur-containing fuel oil is deasphaltedprior to contacting the sulfur-containing fuel oil with the binarycatalyst and oxygen. Deasphalting of the sulfur-containing fuel oil maybe carried out by methods known to one skilled in the art. Typically,deasphalting is carried out by contacting the sulfur-containing fuel oilwith an inert diluent and filtering or centrifuging the resultantmixture to separate the fuel oil from the insoluble asphaltenes toprovide a deasphalted fuel oil. In one embodiment, the inert diluent isselected from the group consisting of liquid saturated hydrocarbons,liquid cyclic hydrocarbons, and mixtures of at least two of theforegoing inert diluents. Suitable non-limiting examples of liquidcyclic hydrocarbons include cyclohexane, cycloheptane, and decalin.Suitable non-limiting examples of liquid saturated hydrocarbons includepropane, butane, and petroleum ether. In one embodiment, the method forpurifying the sulfur-containing fuel oil further comprises a step ofrecovering the inert diluent. In one embodiment, the inert diluent isrecovered from the first oxidized mixture by distillation, using methodsknown to one skilled in the art.

In another embodiment, the present invention provides a method forpurifying a sulfur-containing fuel oil comprising (a) contacting in afirst reaction mixture the sulfur-containing fuel oil with a hydrocarbondiluent, an exogenous binary catalyst, hydrogen peroxide, and awater-soluble acid at a temperature in a range of from about 25° C. toabout 150° C. to provide a first oxidized mixture; and (b) separating atleast one oxidized sulfur compound from the first oxidized mixture; and(c) recovering the hydrocarbon diluent to provide a purified fuel oil.

In yet another embodiment, the present invention provides a method forpurifying a sulfur-containing fuel oil comprising (a) contacting in afirst reaction mixture the sulfur-containing fuel oil comprisingbenzothiophene, dibenzothiophene, alkyl substituted benzothiophenes, andalkyl substituted dibenzothiophenes with petroleum-ether, an exogenousbinary catalyst, hydrogen peroxide, and a water-soluble acid at atemperature in a range of from about 25° C. to about 120° C. to providea first oxidized mixture comprising sulfoxides and sulfones ofbenzothiophene, dibenzothiophene, alkyl substituted benzothiophene, andalkyl substituted dibenzothiophene; (b) separating at least one oxidizedsulfur compound from the first oxidized mixture; and (c) recoveringpetroleum-ether to provide a purified fuel oil.

The following examples are intended only to illustrate methods andembodiments in accordance with the invention, and as such should not beconstrued as imposing limitations upon the claims.

EXAMPLES

Reagents and catalysts employed herein were obtained from AldrichChemical Company.

Examples 1 to 21 and Comparative Examples CE-1 to CE-11 Effect OfOxidative Desulfurization On A Sulfur-Containing Fuel Oil Model Mixture

Two model mixtures were prepared as described below. The first modelmixture was prepared from tetralin and benzothiophene (BT), anddibenzothiophene (DBT) wherein the sulfur-containing compounds werepresent in a 1:2 weight ratio (mixture #1). The second model mixture wasprepared from tetralin and dioctylsulfide (DOS), BT, and DBT wherein thesulfur-containing compounds were present in a 2:2:3 weight ratio(mixture #2). The mixture #1 was used in Examples 1 to 16 andComparative examples 1 to 7. The mixture #2 was used in Examples 17 to19 and Comparative examples 8 to 9. The model mixtures were shown tocomprise about 3 weight percent sulfur, when tested using a VarianSaturn 2000 GCMS.

5 milliliters (ml) of a model mixture, sulfuric acid 0.6 grams (g), acatalyst 50 milligrams (mg) and a co-catalyst 5 to 25 mg; or acombination of 5 ml of model mixture, acetic acid 0.6 g, a cataylst 50mg, and a co-catalyst 5 to 25 mg; or a combination of 5 ml of modelmixture, an acid 0.6 g, a catalyst 50 mg, a co-catalyst 5 to 25 mg, and100 mg of a phase transfer catalyst Aliquat 336™ were placed in two-dramvials equipped with magnetic cross-like stirbars. Hydrogen peroxide (30weight percent, 2 ml) was then added to each of the vials and the vialswere placed in a Thermoline dry block heater and stirrer. The reactionmixture was stirred for about 30 minutes. The vials were removed andcooled in an ice bath. The cooled mixture was filtered through a filterdevice (Whatman autovial 0.45 micron PTFE). The filtrate was collectedin a fresh vial. On standing, the filtrate separated into a top oillayer and a bottom aqueous layer. For analysis, the top oil layer 0.25ml was diluted with 2.25 ml of acetonitrile containing 0.35 weightpercent of biphenyl (internal standard). The diluted oil layer wasanalyzed on the Varian Saturn 2000 GCMS. The results are provided inTable 1, Table 2, and Table 3 below.

TABLE 1 Conversion of BT and DBT in the reaction of oxidation withhydrogen peroxide in the presence of exogenous binary calaysts andsulfuric acid. Co-Catalyst Catalyst-Co- Conversion Percentage ExampleCatalyst Formula mg Catalyst molar ratio DBT DOS 1 Na₂WO₄ Ce(NO₃)₃ 711.9 43.2 82.0 2 Na₂WO₄ (NH₄)Fe(SO₄)₂ 12 6.1 40.9 65.9 3 Na₂WO₄ NiSO₄ 75.7 47.7 81.4 4 Na₂WO₄ Co(OAc)₂ 8 4.7 44.8 80.5 5 (NH₄)₆Mo₇O₂₄ Ce(NO₃)₃13 11.9 65.0 92.9 6 (NH₄)₆Mo₇O₂₄ CoSO4 7 6.3 30.2 98.1 7 MnSO₄(NH₄)Fe(SO₄)₂ 24 5.9 80.0 73.7 8 MnSO₄ NiSO₄ 9 8.6 40.4 24.3 9 MnSO₄Co(OAc)₂ 15 4.9 87.6 70.7 10  MnSO₄ Ce(NO₃)₃ 14 11.6 87.5 38.4 11  MnSO₄KMnO₄ 5 9.3 47.3 43.6 12  NH₄H₂PO₄ CoSO₄ 7 4.8 40.3 55.8 CE-1 Na₂WO₄None — — 35.0 55.7 CE-2 (NH₄)₆Mo₇O₂₄ None — — 56.3 98.6 CE-3 MnSO₄ None— — 21.6 27.3 CE-4 NH₄H₂PO₄ None — — 19.4 15.4

TABLE 2 Conversion of BT and DBT in the reaction of oxidation withhydrogen peroxide in the presence of exogenous binary catalysts andacetic acid. Co-Catalyst Catalyst-Co-Catalyst Conversion PercentageExample Catalyst Formula mg molar ratio DBT DOS 13 MoO₃ (NH₄)Fe(SO₄)₂ 533.1 69.8 67.8 14 NH₄H₂PO₄ CoSO₄ 5 13.5 87.9 17.2 15 NH₄H₂PO₄ NiSO₄ 129.5 88.4 25.3 16 (NH₄)₆Mo₇O₂₄ Ce(NO₃)₃ 13 11.9 48.5 54.4 CE-5 MoO₃ None— — 13.9 16.2 CE-6 NH₄H₂PO₄ None — — 10.8 8.0 CE-7 (NH₄)₆Mo₇O₂₄ None — —34.2 45.6

TABLE 3 Conversion of BT and DBT in the reaction of the oxidation withhydrogen peroxide in the presence of binary catalysts, an acid, and aphase transfer catalyst. Phase Co-Catalyst transfer ConversionPercentage Example Catalyst Formula mg Acid catalyst BT DBT DOS 17(NH₄)₆Mo₇O₂₄ KMnO₄ 5 Sulfuric Yes 69.8 67.8 100 18 (NH₄)₆Mo₇O₂₄ KMnO₄ 5Acetic Yes 87.9 17.2 100 19 (NH₄)₆Mo₇O₂₄ MnSO₄ 6 Sulfuric Yes 83.0 99.7100 20 (NH₄)₆Mo₇O₂₄ MnSO₄ 6 Acetic Yes 81.0 99.8 100 21 (NH₄)Fe(SO₄)₂CoSO₄ 9 Acetic Yes 88.4 25.3 87.5 CE-8 (NH₄)₆Mo₇O₂₄ KMnO₄ 5 Sulfuric No48.5 54.4 14.6 CE-9 (NH₄)₆Mo₇O₂₄ KMnO₄ 5 Acetic No 16.0 4.4 8.3 CE-10(NH₄)₆Mo₇O₂₄ MnSO₄ 6 Sulfuric No 56.4 86.9 99.8 CE-11 (NH₄)₆Mo₇O₂₄ MnSO₄6 Acetic No 30.0 50.1 99.7

Examples 1 to 21 demonstrate that the process disclosed herein,generally affords satisfactory sulfur removal of greater than about 85percent. Further, catalyst activity appears to be dependent on themolecular structure of the catalyst. On comparing the conversionefficiency of catalysts in Tables 1 and 2, it can be seen that thebinary catalysts having the following combinations Mo/Fe, P/Co, and P/Nidemonstrate good catalytic activity in the presence of acetic acid,while binary catalysts having the following combinations Mo/Ce, Mo/Ni,and Mn/Co demonstrate good catalytic activity in the presence ofsulfuric acid. Furthermore, at least as seen in Examples 9 and 10 andComparative examples CE-2 the use of binary catalysts significantlyimproves the conversion of the most difficult to oxidizesulfur-containing compound BT from about 56 percent in the absence ofthe catalyst to about 87 percent in the presence of the catalyst. Also,as seen in Table 3, Examples 17 to 21, use of a phase transfer catalystdemonstrates significant improvement in the conversion of all the sulfurcompounds used to prepare the model fuel mixtures.

Examples 22 to 26 and Comparative Examples CE-12 to CE-13 Effect OfOxidative Desulfurization On A Sulfur-Containing Distillate Fuel Oil

25 ml of Saudi Crude atmospheric distillate fraction 600-700° F.(315-370° C.), containing 2.255 weight percent sulfur, is first mixedwith sulfuric or acetic acid and a binary catalyst consisting of about250 mg of the first component and about 50 mg of the second componentand placed into a reaction flask. Hydrogen peroxide (30 weight percent)is then added sequentially in three portions by 3 ml to the flask understirring. The reaction mixture is stirred for about 30 minutes. Themixture is centrifuged and the oil layer is separated from the aqueousone. The oil layer is washed with 10 ml of acetonitrile to removeoxidized products. The oil layer is analyzed on the Spectro Phoenix IIXRF analyzer. The results are provided in Table 4 below. In general, theoxidized sulfur compounds may be separated from the crude oil containingreaction mixture (first oxidized mixture) using any of the techniquesdisclosed herein as being effective for that purpose.

TABLE 4 Sulfur removal from distillate fuel oil and oil yield in thereaction of the oxidation with hydrogen peroxide in the presence ofbinary catalyst, an acid, and a phase transfer catalyst. Sulfur in Phasetreated Sulfur Oil Co-Catalyst transfer oil, removal, yield, ExampleCatalyst Formula mg Acid catalyst perent percent percent 22 MnSO₄Co(OAc)₂ 53 Sulfuric No 0.49 78.2 59.1 23 (NH₄)₆Mo₇O₂₄ Ce(NO₃)₃ 51Sulfuric No 0.40 82.3 83.5 24 (NH₄)₆Mo₇O₂₄ MnSO₄ 52 Acetic No 1.47 34.886.0 25 (NH₄)₆Mo₇O₂₄ MnSO₄ 52 Acetic Yes 1.29 42.8 84.0 CE-12 MnSO₄ None— Sulfuric No 1.03 54.3 85.1 CE-13 (NH₄)₆Mo₇O₂₄ None — Sulfuric No 0.4181.8 50.4

Examples 22 to 25 also demonstrate that the process disclosed herein,generally applicable to real oil distillates and affords satisfactorysulfur removal of greater than about 80 percent at satisfactory fuel oilyield. On comparing the ODS process efficiency of binary catalysts inexamples 22 and 23 and single component catalysts in comparativeexamples CE-12 and CE-13, it can be seen that the binary catalyst havingthe combination Mn/Co demonstrates noticeable improvement in sulfurremoval, while binary catalyst having the combination Mo/Ce demonstratessignificant improvement of the process selectivity and the fuel oilyield. Furthermore, as seen in comparing Examples 24 and 25, the use ofa phase transfer catalyst significantly improves the sulfur removal froma fuel oil at about the same oil yield in that is obtained in thepresence of acetic acid. It should be noted that the experimentsconducted as part of this study were not optimized in all cases. Thus itis believed that much higher conversion of sulfur compounds that thoseshown in Table 1, 2, 3 and 4 are achievable, by adjusting variousreaction parameters which are known to those skilled in the art. Suchoptimization falls within the scope of the instant invention.

In each of Examples 1 to 25 the oxidized sulfur compounds may beseparated from the reaction mixture (first oxidized mixture) using anyof the techniques disclosed herein as being effective for that purpose.In one embodiment, the reaction mixture of Example 1 is filtered througha pad of silica gel to remove both the oxidized sulfur compounds and theexogenous binary catalyst which may be recovered therefrom.

The foregoing examples are merely illustrative, serving to illustrateonly some of the features of the invention. The appended claims areintended to claim the invention as broadly as it has been conceived andthe examples herein presented are illustrative of selected embodimentsfrom a manifold of all possible embodiments. Accordingly, it isApplicants' intention that the appended claims are not to be limited bythe choice of examples utilized to illustrate features of the presentinvention. As used in the claims, the word “comprises” and itsgrammatical variants logically also subtend and include phrases ofvarying and differing extent such as for example, but not limitedthereto, “consisting essentially of” and “consisting of.” Wherenecessary, ranges have been supplied, those ranges are inclusive of allsub-ranges there between. It is to be expected that variations in theseranges will suggest themselves to a practitioner having ordinary skillin the art and where not already dedicated to the public, thosevariations should where possible be construed to be covered by theappended claims. It is also anticipated that advances in science andtechnology will make equivalents and substitutions possible that are notnow contemplated by reason of the imprecision of language and thesevariations should also be construed where possible to be covered by theappended claims.

1. A method for purifying a sulfur-containing fuel oil, the methodcomprising: (a) contacting in a first reaction mixture thesulfur-containing fuel oil with an exogenous binary catalyst, hydrogenperoxide and a water-soluble acid, at a temperature in a range of fromabout 25° C. to about 120° C. to provide a first oxidized mixture; and(b) separating at least one oxidized sulfur compound from the firstoxidized mixture to provide a purified fuel oil.
 2. The method accordingto claim 1, wherein the sulfur-containing fuel oil comprises less than 5weight percent sulfur.
 3. The method according to claim 1, wherein thesulfur-containing fuel oil comprises less than 3 weight percent sulfur.4. The method according to claim 1, wherein the exogenous binarycatalyst comprises a first component selected from the group consistingof phosphate salts, and oxides, acids and salts of molybdenum, tungsten,manganese, and combinations thereof, and a second component selectedfrom the group consisting of oxides and salts of cerium, iron, vanadium,titanium, manganese, cobalt, nickel, copper and combinations thereof. 5.The method according to claim 4, wherein the first component comprisesan oxide or a salt of manganese.
 6. The method according to claim 4,wherein the second component comprises an oxide or a salt of cobalt. 7.The method according to claim 4, wherein the second component comprisesan oxide or a salt of cerium.
 8. The method according to claim 4,wherein the second component comprises an oxide or a salt of iron. 9.The method according to claim 4, wherein the exogenous binary catalystcomprises oxides, acids or salts of molybdenum as the first componentand oxides or salts of cerium as the second component.
 10. The methodaccording to claim 4, wherein the exogenous binary catalyst comprisesoxides or salts of manganese as the first component and oxides or saltsof iron, cobalt, or nickel as the second component.
 11. The methodaccording to claim 4, wherein the exogenous binary catalyst comprisesphosphate salts as the first component and oxides or salts of iron,cobalt, or nickel as the second component.
 12. The method according toclaim 4, wherein the first component comprises an oxide, an acid or asalt of molybdenum.
 13. The method according to claim 12, wherein thefirst component comprises a molybdenum isopolyacid or its salt.
 14. Themethod according to claim 1, wherein the sulfur-containing fuel oil isdeasphalted prior to contacting the sulfur-containing fuel oil with thebinary catalyst, hydrogen peroxide and the water-soluble acid bycontacting the sulfur-containing fuel with an inert diluent.
 15. Themethod according to claim 1, wherein the water-soluble acid is selectedfrom the group consisting of formic acid, acetic acid, propionic acid,butyric acid, sulfuric acid, phosphoric acid, and mixtures of two ormore of the foregoing acids.
 16. The method according to claim 1,wherein the separating is carried out using solid-liquid extraction. 17.The method according to claim 1, wherein the separating is carried outusing liquid-liquid extraction.
 18. The method according to claim 1,wherein the sulfur-containing fuel oil comprises benzothiophene,dibenzothiophene, alkyl substituted benzothiophenes, and alkylsubstituted dibenzothiophenes.
 19. The method according to claim 1,further comprising a step of recovering the binary catalyst.
 20. Themethod according to claim 1, wherein the first reaction mixture furthercomprises a phase transfer catalyst.
 21. The method according to claim20, wherein the phase transfer catalyst comprises a quaternary ammoniumsalt or a quaternary phosphonium salt.
 22. A method for purifying asulfur-containing fuel oil, the method comprising: (a) contacting in afirst reaction mixture the sulfur-containing fuel oil with a hydrocarbondiluent, an exogenous binary catalyst, hydrogen peroxide, and awater-soluble acid at a temperature in a range of from about 25° C. toabout 110° C. to provide a first oxidized mixture; (b) separating atleast one oxidized sulfur compound from the first oxidized mixture; and(c) recovering the hydrocarbon diluent to provide a purified fuel oil.23. The method according to claim 22, wherein the exogenous binarycatalyst comprises a first component selected from the group consistingof phosphate salts, and oxides, acids and salts of molybdenum, tungsten,manganese, and combinations thereof, and a second component selectedfrom the group consisting of oxides and salts of cerium, iron, vanadium,titanium, manganese, cobalt, nickel, copper and combinations thereof.24. A method for purifying a sulfur-containing fuel oil, the methodcomprising: (a) contacting a sulfur-containing fuel oil comprisingbenzothiophene, dibenzothiophene, alkyl substituted benzothiophenes, andalkyl substituted dibenzothiophenes with petroleum-ether, a exogenousbinary catalyst, and oxygen at a temperature in a range of from about25° C. to about 120° C., and at a pressure in a range of from about 1atmosphere to about 150 atmospheres to provide a first oxidized mixturecomprising sulfoxides and sulfones of benzothiophene, dibenzothiophene,alkyl substituted benzothiophenes, and alkyl substituteddibenzothiophenes; (b) separating at least one oxidized sulfur compoundfrom the first oxidized mixture; and (c) recovering petroleum-ether toprovide a purified fuel oil.
 25. The method according to claim 24,wherein the exogenous binary catalyst a first component selected fromthe group consisting of phosphate salts, and oxides, acids and salts ofmolybdenum, tungsten, manganese, and combinations thereof, and a secondcomponent selected from the group consisting of oxides and salts ofcerium, iron, vanadium, titanium, manganese, cobalt, nickel, copper andcombinations thereof.